1. Field of the Invention
The invention relates to the field of communication. More specifically, the invention relates to communication networks.
2. Background of the Invention
The multi-protocol label switching (MPLS) protocol may be categorized as a network layer protocol of the Open Standards Institute (OSI) reference model. MPLS provides a method for generically tunneling data through networks with label switched paths (LSPs). Traffic travels along an LSP with label stacks.
FIG. 1 (Prior Art) is a diagram of a label stack entry according to multi-protocol label switching (MPLS). A label stack entry 100 is a 32-bit value that includes the following fields: a label identifier field 101, a stack bit field 103, an experimental field 105, and a time to live field (TTL)107. The label identifier field 101 includes a 20-bit label identifier for a label switched path (LSP). The stack bit field 103 includes a single bit to indicate whether the label stack entry 100 is the last label stack entry of a packet. The experimental field 105 includes 3 bits reserved for experimental purposes. The time to live field 107 includes 8 bits to indicate the number of hops a label stack entry should exist.
Typically, a client (e.g., a signaling protocol module) requests a label identifier. A centralized process allocates a label identifier from a label space by traversing an array of label identifiers previously allocated from the label space. Once the allocated label identifiers are determined, a free label identifier is allocated. Traversing such an array of previously allocated labels is inefficient. As the number of allocated labels increases, label allocation performance deteriorates. In addition, allocating labels from a centralized array of label identifiers for a label space, prevents continued forwarding of packets along an LSP of a signaling protocol module that has restarted.